[llvm] [DebugInfo][NVPTX] Adding support for `inlined_at` debug directive in NVPTX backend (PR #170239)

[Jeremy Morse via llvm-commits]

jmorse wrote:

There's some discussion elsewhere about how NVPTX can/might produce a two-level-line-table, similar to [the past DWARF propoosal](https://dwarfstd.org/issues/140906.1.html) -- is part of the rationale behind tracking already-emitted-locs to do with referring to the linetable row where something was inlined from? I can see how you'd want to determine a cannonical "inlined from here" row to support that. If that's the motivation, we just need to explain it in the comments.

https://github.com/llvm/llvm-project/pull/170239